The present invention relates to improvement of a free-ink collector type writing instrument having a point assembly as a writing portion at the tip, such as a ball-point pen, felt pen, fountain pen, etc., comprised of an ink tank for storing ink directly, a collector as an adjuster made up of multiple vanes for adjusting the internal pressure using capillary action, a means for feeding ink from the ink tank to the point assembly. The present invention particularly relates to improvement against deficiencies immediately after production and improvement of the collector in the internal pressure adjusting function to deal with change in temperature and change in pressure during use.
Writing instruments which have a collector disposed between a point assembly and ink tank for retaining free-state ink and regulating the pressure inside the ink tank so as to prevent ink leakage from the pen tip and ink from flooding from an air hole have been conventionally known.
There have also been known so-called sliver type pens which have a sliver of fabric bundles impregnated with a low viscosity ink of some mPaxc2x7s and an ink feed for feeding ink to their pen point. This sliver type pen, however, has the problem of ink consumption being indiscernible and the problem that an ample amount of ink flows out, and hence thick drawn lines can be obtained, in the starting stage but the flow amount gradually becomes lower, and hence the drawn lines become thinner, as the ink is used for writing. In order to smoothly deliver the ink from the sliver, the capillary capacity of the sliver may be set to be low. However, this setting will increase the occurrence of ink leakage and eruption from the sliver and smudging clothes due to impacts such as from being dropped. In contrast, if the capillary capacity of the fabric sliver is increased, there occurs an ink ejection problem in that the ink flow rate sharply lowers as the ink is used for writing and the drawn lines become considerably thin in the latter half of its life even though there is still an abundant amount of ink left.
A collector writing instrument has some advantages that it delivers ink at a flow rate equal to or above that of a sliver type writing instrument at the starting stage and will not gradually reduce its ink flow rate and is able to provide thick lines even without applying any extra writing force until its life""s end, that it can be charged with a large amount of ink and that the amount of free-state ink left can be checked.
As shown in FIGS. 7 and 8, in a collector writing instrument, once air inside ink tank 3 expands or contracts due to variation of the external air in pressure or due to change in temperature, ink 2 moves between collector 6 and ink tank 3 (or air enters the tank through a narrow ink channel 14 and air/liquid exchanger 18) so as to adjust the internal pressure, whereby it is possible to prevent ink 2 from leaking out from the tip 9 of a point assembly 1. Since, if the capacity of ink tank 3 is large the expansion/contraction of the air space in tank 3 becomes large, a certain relationship has been found between the capacity of ink tank 3 and the maximum ink retention capacity of collector 6. Conventionally, there has been completed inventions and commercial products which use a collector having a capacity of about 10% or more of the ink tank capacity.
There exist some collector writing instruments which bring about a flooding problem if reduction and increase in pressure due to change in temperature, variation in pressure, change in altitude or any other change is repeated. However, conventionally, if the performance of a collector writing instrument under a temperature rise from room temperature at about 20xc2x0 C. to about 50xc2x0 C., which is conceivably the maximum atmospheric temperature, is validated, the writing instrument is considered as having a good performance free from problems. However, in the cases where a writing instrument which has been put under winter ambient air is carried to the front of a heater, the writing instrument will undergo a sharp temperature rise from 0xc2x0 C. to 50xc2x0 C. In such a case, the conventional writing instruments would cause ink flooding and other problems.
In order to solve the flooding problem, some countermeasures can be considered such as enlarging the maximum ink retention of collector 6 (making the diameter or length greater), reducing the size of ink tank 3 and other methods. However, all these methods have some drawbacks: that is, a style problem due to enlargement of the barrel size; lowering of cost performance due to reduction in ink amount and hence short life; and the problem of forward leakage being likely to occur due to a too long collector 6 or a too long distance from air/liquid exchanger 18 to tip 9 of point assembly 1 (to be called xe2x80x98ink head Hxe2x80x99 hereinbelow). Alternatively, to reach a solution with ink 2, an ink 2 has to have an extremely low wetting ability, which means compromising the writing performance.
On the other hand, when a collector writing instrument which has been capped under about 1 atm. on the ground and is uncapped inside an airplane in which the air pressure is generally reduced to about 0.8 atm., the interior of the pen which has been balanced under 1 atm., is instantaneously exposed to an environment of about 0.8 atm., so ink 2 inside moves in a rush through an air groove 15 inside collector 6, whereby ink 2 floods out from an air hole 10, being unable to be properly retained by the whole part of retaining grooves 13.
In order to solve the flood problem occurring under conditions in which the air pressure varies, devices and inventions have been disclosed in Japanese Utility Model Publication Hei 3 No. 31580, Japanese Utility Model Publication Laid-open Hei 3 No. 31581 and Japanese Patent Application Laid-open Hei 9 No. 104194, and others. However, these disclosures only provide the function of slightly weakening the flush inside the collector.
A collector writing instrument is configured so that air/liquid exchanger 18 is wetted with ink 2 and ink 2 or air is replaced only through air/liquid exchanger 18 having a high enough capillarity. A collector writing instrument is one which makes use of the mechanism that the internal pressure on the ink tank 3 side is substantially reduced by the function of a meniscus formed by the capillarity of air/liquid exchanger 18 to prevent ink 2 from flowing out even when it is oriented downwards.
For this reason, it is necessary to wet air/liquid exchanger 18 near the rear end of collector 6 and partitioning portion 19 around the exchanger at almost the same time when assembled. If this wetting with ink 2 is not enough to fully create shutoff, air will flow into the ink tank 3 side other than through air/liquid exchanger 18 so that the reduction of ink tank 3 in pressure by the function of the meniscus cannot be achieved. This results in a deficiency in that the ink 2 leaks to point assembly 1 or the retaining portion of collector 6 without a break. Conventionally, impacts used to be applied immediately after assembly to wet the rear end portion, or the instrument used to be left to stand with its pen tip set downward for a certain period of time to fully wet the rear end portion. However, these production processes have so far entailed insufficiency of wetting, a necessity of long period of time in production and other drawbacks.
Enhancement of the resistance against flooding can be achieved by increasing the capacity of collector 6. However, if collector 6 is made longer to avoid the thickness problem, the ink head H applying on the point assembly becomes higher, whereby a forward leakage problem, i.e., the problem of ink 2 leaking out from point assembly 1 occurs. Therefore, it has been impossible in conventional configurations to simply make collector 6 longer to increase the capacity of collector 6.
In order to improve the resistance against flooding, the applicant hereof has made a device having a longer collector without increase in collector head. However, since this configuration has a greater area to be wetted with ink for shutoff immediately after the production of the air/liquid exchanger and its vicinity, there is a demand for a solution to the problem during manufacturing.
Further, a solution to an ink flooding problem due to a sharp variation in pressure such as on an airplane has been demanded. Especially, due to repetitions of sharp variations in pressure, ink 2 is caused to be left behind inside retention grooves 13 of collector 6 and this left ink may flood out even by a slight temperature rise or other reasons. A countermeasure against this problem is also demanded. However, there has been no proposal of collector type writing instruments which is able to meet the above demands without any compromise in other performances.
It is therefore a main object of the present invention to provide improvement of collector type writing instruments of present types, it is an object to provide a collector type writing instrument which can avoid crucial malfunctions such as pollution of consumer""s clothes, by improving the prevention capability against accidents in handling of writing instruments, such as the ink leakage defect due to influence of increase and reduction in pressure inside ink tank 3 caused by temperature changes and air pressure changes, the flooding problem occurring when they have been stocked for long periods in shops, the ink forward leakage defect, the ink flooding problem during manufacturing, and other problems.
It is a further object to provide a collector type writing instrument which meets the demands for slim appearance of a collector type, which tends to become thick, without compromising the excellent writing comfort attributed to conventional collector writing instruments and without increasing its cost.
In sum, it is an object to provide a writing instrument which is free from the forward leakage problem even when the capacity of collector 6 is increased and to provide a collector type writing instrument free from the problem of ink 2 flooding when increase and reduction in pressure is repeated. In particular, it is an object to achieve a task of returning ink 2, inside collector 6, to the tank 3 side under an environment in which sharp changes in pressure occur and reach a solution to a problem of difficulties in shutting off ink tank 3 from the outside air because of unwillingness of partitioning portion 19 and air/liquid exchanger 18 to get wetted with ink during assembly due to enlargement of the areas of other parts (such as partitioning portion 19) than air/liquid exchanger 18.
The collector writing instruments of the present invention include ball-point pens which have an ink feeder portion such as an ink feeder core (center core 8 and/or collector core 7) functioning based on capillarity to assure a flow passage from an ink tank 3 to a writing point 9 provided at the tip of a point assembly 1 and felt tip pens, markers and the like of which the ink feeder core 7 or 8 itself serves as a point assembly 1. Hereinbelow, ink feeder cores (center core 8, collector core 7, etc.) will also include those which themselves serve as pen tips.
Arranged between ink tank 3 of a cup-like shape with a bottom and point assembly 1 is a collector 6a, which includes a vent channel 11 connected to the outside air and air grooves 15, an air/liquid exchanger 18, an elongated ink groove 14, a plurality of retaining grooves 13, 13a, defined as the gaps between vanes 12, 12a, arranged at intervals determined as appropriate, and has the function of controlling the internal pressure inside the pen body by allowing ink 2 to flow into and out of retaining grooves 13, 13a. 
As the first means of the present invention, also-called collector type writing instrument is comprised of: a point assembly having a writing point at the front end thereof; an ink tank for storing free-state, relatively low-viscosity ink having a viscosity of 2 to 100 mPaxc2x7s at normal temperature; a feeder portion such as a center core and the like for feeding ink from the ink tank to the writing point; and a collector made up of a plurality of vane-like adjusting elements for adjusting the internal pressure of the ink tank by making use of capillary capacity and a longitudinal groove serving as an air/liquid exchanger groove and connected to the vane-like adjusting elements, and is characterized in that: the collector has a partitioning portion comprised of a frontmost partitioning portion capable of shutting off air communication between the ink tank and the outside air other than through the air/liquid exchanger, a rearmost partitioning portion and connecting partitioning portions for connection between the frontmost partitioning portion and the rearmost partitioning portion; main retaining grooves are formed from the frontmost partitioning portion toward the point assembly side; auxiliary retaining grooves are formed between the frontmost partitioning portion and the rearmost partitioning portion; air grooves connected to the outside air are formed in both the auxiliary retaining grooves and the main retaining grooves; an air/liquid exchanger and a narrow groove for leading ink to the air/liquid exchanger are formed between the frontmost partitioning portion and the rearmost partitioning portion; and lateral grooves for leading ink from the narrow groove to the connecting partitioning portions are provided.
Usually, a partitioning portion 19 is formed on the outer periphery of the collector, as shown in FIG. 8, so as to enclose the collector on the same plane that is perpendicular to the axial direction. In the present invention, instead of arranging a partitioning portion 19A on the same plane that is perpendicular to the axial direction as such, it is arranged extending partly towards the point assembly side, displacing from the outer periphery of the collector or the axial direction. The frontmost partitioning portion indicates the partitioning portion 19c which is the closest to the point assembly side with respect to the axial direction, and the rearmost partitioning portion indicates the partitioning portion 19d which is the closest to the ink tank side with respect to the axial direction. Connecting partitioning portions 19a are provided for connection between frontmost partitioning portion 19c and rearmost partitioning portion 19d. Formed between frontmost partitioning portion 19c and rearmost partitioning portion 19d are an air/liquid exchanger 18 and a narrow groove 21 for leading ink to the air/liquid exchanger while lateral grooves 22 for leading ink from the narrow groove 21 to connecting partitioning portions 19a are provided. This arrangement makes it possible to lead ink from the narrow groove to connecting partitioning portions 19a via the lateral grooves. As a result, the whole partitioning portion 19A including connecting partitioning portions 19a can be positively wetted, whereby it is possible to surely shut off the ink tank from the outside air. Further, in order to enhance wetting with ink 2, chamfers 24 may be formed near lateral grooves 22 (see FIG. 3).
When ink wets the connecting partitioning portions, the ink at the connecting partitioning portions is drawn into the auxiliary retaining grooves because the auxiliary retaining grooves themselves have capillary capacity. In sum, when the connecting partitioning portions are wetted, ink can be held within the auxiliary retaining grooves.
Accordingly, in order to lead ink into the auxiliary retaining grooves, it is not always necessary to provide partitioning portion grooves 23, which will be described later.
As the methods considered for leading ink from the connecting partitioning portions to the auxiliary retaining grooves in a more efficient manner, chamfers 24 may be formed in the connecting partitioning portions so that, when the connecting partitioning portions get wetted with ink, ink can be led into the auxiliary retaining grooves by capillary capacity. Alternatively, any shape and configuration such as grooves, cutouts, holes, gaps defined by combination of a plurality of parts, which can in essence lead ink 2 to the auxiliary retaining grooves, may be formed in the connecting partitioning portions.
The head acting on the point assembly is calculated based on the position of the air/liquid exchanger. In the present invention, the auxiliary retaining grooves are formed from this air/liquid exchanger toward the ink tank side so that ink can be retained therein. In general, increase in the ink retention of a collector may be made by increase in length of the collector, however this may be accompanied with a risk of ink leakage from the pen tip because the head also is increased. However, the arrangement of the present invention in which auxiliary retaining grooves, connecting partitioning portions and lateral grooves and the like are formed from the air/liquid exchanger toward the ink tank side makes it possible to increase the ink retention of the collector without any head increment (without increasing the risk of ink leakage from the pen tip).
As the second effective means of the present invention, collector 6a is comprised of conventionally known, main retaining grooves 16 having a function of internal pressure adjustment, in the front side of the collector confronting the point assembly 1 and auxiliary retaining grooves 17 at the rear of the former in order to increase the ink retention. Further, partitioning portion 19d and extended partitioning portion 19e and 19f, which are extended in the axial direction, are provided, whereby ink tank 3 can be virtually shut off from the outside air when both the above portions and air/liquid exchanger 18 are wetted with ink 2. Main retaining grooves 16 are disposed more frontward or closer to the point assembly 1 side, than extended partitioning portion 19e and 19f while auxiliary retaining grooves 17 are disposed around the extended partitioning portion 19e which is axially extended, in the circumferential direction. The part with hatching shown in FIG. 2 and air/liquid exchanger 18 are wetted with ink 2 to shut off the external air.
Further, a certain space (width) is created in an enclosed portion 19b, so that air bubbles arising from air/liquid exchanger 18 can easily move into ink tank 3.
Air grooves 15 connected to the outside air are formed in both auxiliary retaining grooves 17 and main retaining grooves 16 while a narrow groove 21 and lateral grooves 22 which lead ink 2 from the narrow groove to auxiliary retaining grooves 17 which are connected to extended partitioning portion 19e that is extended axially are formed in enclosed portion 19b. Further, air/liquid exchanger 18 is provided. Lateral grooves 22 may be formed by any shape and configuration such as grooves, cutouts, holes, gaps defined by combination of a plurality of parts, which can in essence lead ink 2 as long as they can provide the function of creating communication of ink 2 led through narrow groove 21 from the ink tank side 3 with extended partitioning portion 19e that is axially extended and auxiliary retaining grooves 17.
Partitioning structure 19 is usually formed on the outer periphery of the collector as shown in FIG. 8, so as to enclose the outer periphery of the collector on the same plane that is perpendicular to the axial direction. Extended partitioning portion 19e and 19f will be described. The extended partitioning portion refers to the portion which are extended partly towards the point assembly side, displacing from the outer periphery of the collector, as will be described in the embodiment hereinbelow.
The way of extension should not be limited to the approximately square bracket-shaped configuration shown in the present embodiment, but semicircular, semi-elliptic, trapezoidal, inverted trapezoidal, V-shaped and other configurations may be employed.
The enclosed portion refers to the portion enclosed by extended partitioning portion 19e and 19f. 
As air/liquid exchanger 18 is formed in enclosed portion 19b defined by extended partitioning portion 19e and 19f, a certain space (width) needs to be formed into enclosed portion 19b in order to permit air bubbles arising from the air/liquid exchanger to move into the ink tank. Since the size of air bubbles arising from an air/liquid exchanger depends on the size of the air/liquid exchanger, it should be determined appropriately depending on the size of the air/liquid exchanger.
When ink wets the extended partitioning portion, the ink in extended partitioning portion 19e that is axially extended is drawn into auxiliary retaining grooves 17 because the auxiliary retaining grooves 17 themselves, which are arranged around extended partitioning portion 19e in the circumferential direction, have capillary capacity. Therefore, when the extended partitioning portion 19e gets wetted, ink can be held within auxiliary retaining grooves 17.
As the methods considered for leading ink from the extended partitioning portion 19e to the auxiliary retaining grooves in a more efficient manner, chamfers may be formed in the extended partitioning portion 19e so that, when the extended partitioning portion 19e is wetted with ink, ink can be led into the auxiliary retaining grooves by capillary capacity. Alternatively, any shape and configuration such as grooves, cutouts, holes, gaps defined by combination of a plurality of parts, which can in essence lead ink 2 to the auxiliary retaining grooves, may be formed in extended partitioning portion 19e and 19f. 
The head acting on the point assembly is calculated based on the position of the air/liquid exchanger. Also in the present invention, the auxiliary retaining grooves are formed from this air/liquid exchanger toward the ink tank side so that ink can be retained therein. In general, increase in the ink retention of a collector may be made by increase in length of the collector, however this may be accompanied with a risk of ink leakage from the pen tip because the head is also increased. However, the arrangement of the present invention in which auxiliary retaining grooves, partitioning portions and lateral grooves and the like are formed from the air/liquid exchanger toward the ink tank side makes it possible to increase the ink retention of the collector without any head increment (without increasing the risk of ink leakage from the pen tip).
The other components used here may employ conventionally publicly known items. For example, as ink 2, a pseudo-plastic ink (also called gel ink) which has a low (or medium) viscosity of 2 to 100 mPaxc2x7s at normal temperature (about 23xc2x0 C.) and presents a rather high viscosity in the static state so as to prevent forward leakage of ink 2 from tip 9 and lowers its viscosity when affected by shearing force or movement while writing so as to enable smooth writing, may be used by modifying it to have a lower viscosity to some degree. Also, various types of publicly known inks using pigments or dyes, which are applicable to collector writing instruments can be appropriately used as ink 2. Similarly, for other components, conventionally used items can be selected as appropriate, such that center core 8 and collector core 7 (these may be used to serve as a writing point in the case of a felt pen or marker) may be of a fiber bundle core made up of fabric threads shaped by heat or adhesives, of a so-called plastic core formed by extrusion molding having a snow-crystal section, of a sintered core made up of small particles with pores therein, thermally fixed or bonded with adhesives, or of a sponge, as long as it is capable of holding and leading ink to a certain degree or more.
The third effective means of the present invention is characterized in that the connecting partitioning portions or the extended partitioning portion has partitioning portion grooves connected to the auxiliary retaining grooves so that the narrow groove, lateral grooves, partitioning portion grooves and auxiliary retaining grooves permit ink to communicate among themselves.
Since connecting partitioning portions 19a or extended partitioning portion (19e, 19f) is formed with partitioning portion grooves connected to the auxiliary retaining grooves so that the narrow groove, lateral grooves, partitioning portion grooves and auxiliary retaining grooves permit ink to communicate between themselves, when a change in internal pressure inside the ink tank occurs, ink is able to smoothly flow from the ink tank to the auxiliary retaining grooves or from the auxiliary retaining grooves to the ink tank, because ink flows not only through connecting partitioning portions 19a and extended partitioning portion 19e and 19f, but also through the partitioning portion grooves.
The fourth effective means of the present invention is characterized in that the vertical sectional area of each partitioning portion groove (cut in the longitudinal direction of the writing instrument) is equal to or smaller than the cross-sectional area of the air/liquid exchanger (sliced along the diametric direction of the writing instrument), and the total of all the vertical sectional areas of the individual partitioning portion grooves is designed to be greater than the cross-sectional area of the air/liquid exchanger.
The vertical sectional area of each partitioning portion groove indicates the area of each partitioning portion groove when the partitioning portion groove is cut by a plane including the axis of the writing instrument.
The cross-sectional area of the air/liquid exchanger indicates the area of the air/liquid exchanger, sliced by a plane perpendicular to the axial direction of the writing instrument.
Since the vertical sectional area of each partitioning portion groove is made equal to or smaller than the cross-sectional area of the air/liquid exchanger, there is difference in capillary capacity produced by ink meniscus between each partitioning portion groove and the air/liquid exchanger. In this case, the capillary capacity generated by each partitioning portion groove is greater. Therefore, air replacement occurs at the air/liquid exchanger during writing and hence it is possible to prevent occurrence of air replacement through each partitioning portion groove. Further, since the total of all the vertical sectional areas of the individual partitioning portion grooves is designated to be greater than the cross-sectional area of the air/liquid exchanger, the flow passage into the auxiliary retaining grooves is greater than the flow passage of the air/liquid exchanger, whereby, when air inside the ink tank expands, it is possible to flow ink into the auxiliary retaining grooves by way of the partitioning portion grooves, more easily than ink flows to the air/liquid exchanger.
The fifth effective means of the present invention is characterized in that the lateral grooves and auxiliary retaining grooves are formed so as to have approximately the same width with respect to the longitudinal direction of the writing instrument.
Since the lateral grooves and auxiliary retaining grooves are formed so as to have approximately the same width, in both cases where ink flows into the auxiliary retaining grooves upon increase in pressure inside the ink tank and where ink returns from the auxiliary retaining grooves into the ink tank upon reduction in pressure inside the ink tank, ink can smoothly flow (if they have different groove widths, ink flows more easily in one direction than in the other direction). Accordingly, it is possible to establish a more efficient ink communication between the auxiliary retaining grooves and the ink tank.
The sixth effective means of the present invention is characterized in that the maximum ink retention xe2x80x98iexe2x80x99 of the auxiliary retaining grooves and the maximum ink retention xe2x80x98isxe2x80x99 of the main retaining grooves are designed so as to satisfy a relation xe2x80x98is greater than ie greater than 0.05xc2x7isxe2x80x99.
The sixth effective means of the present invention is featured by that the maximum ink retention xe2x80x98iexe2x80x99 of auxiliary retaining grooves 17 and the maximum ink retention xe2x80x98isxe2x80x99 of main retaining grooves 16 are designed so as to satisfy a relation xe2x80x98is greater than ie greater than 0.05xc2x7isxe2x80x99 (preferably xe2x80x980.3xc2x7is greater than ie greater than 0.1xc2x7isxe2x80x99).
The dimensions of main retaining grooves 16, such as the length, capacity and the like, are in effect determined by ink head H, the size of air/liquid exchanger 18 (vertical groove width and hole size) and the capacity of ink tank 3. When the outside diameter of collector 6 is assumed, as is usual, to be uniform, the summation of the axial lengths of auxiliary retaining grooves 17 should be smaller than the summation of the axial lengths of main retaining grooves 16 and should be set to be equal to or greater than 5% of the summation of the axial lengths of main retaining grooves 16.